Document Details Page

See also data package with Excel files for the appendices: http://www.trrp.net/library/data?id=105

 

From the Executive Summary:

 

This report presents the results of Water Year (WY) 2017 sediment transport monitoring efforts on the Trinity River near Weaverville, California. As part of an ongoing study for the Trinity River Restoration Program (TRRP), GMA Hydrology (GMA, formerly Graham Matthews and Associates) conducted bedload and suspended sediment sampling at four monitoring locations. Secondary hydrologic and geomorphic data such as water surface slope, streamflow measurements, cross section surveys, pebble counts and turbidity were collected as part of the study. New for 2017 was: (1) bulk sampling, pebble counts, bed elevation and scour monitors at bars upstream of sampling sites, (2) reduced effort at the Lewiston site, (3) suspended sediment sampling effort was reduced, and (4) partitioned bedload data were provided for the Lewiston and Douglas City sites to support hydroacoustic computations. WY2017 marks the 13th year (2004-2013, 2015-2017) of Trinity River sediment transport monitoring by GMA Hydrology for TRRP. 

 

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This 2017 study is conducted as part a sediment budget approach to understanding sediment-related habitat issues. We provide sediment load estimates at four locations along the river: at Lewiston (TRAL), near Grass Valley Creek (TRGV), at Limekiln Gulch (TRLG), and near Douglas City (TRDC). The sediment load estimates inform gravel injection strategies (locations and volumes) and hydrograph development for Spring Flow Releases.

 

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WY2017 was determined to be an “Extremely Wet” water year (TRRP 2017). A two-week long 1,530 cfs flow bench (April 5 to April 19) preceded the planned Spring Flow Release. The approved release hydrograph (mean daily flows) included a 5 day rise from base flow to 11,000 cfs. The planned peak included two days of 11,000 cfs and one day of 10,000 cfs. A sharp decline over 5 days to approximately 2,500 cfs was to be followed by 5 days of approximately 2,500 cfs. A second bench of 4,800 to 5,400 cfs was to begin May 10 and last for 9 days. A gradual tailout spanned most of the summer with the hydrograph dropping back to summer base (450 cfs ) in mid August.

 

This “double peaked” hydrograph was the second of this type to be implemented for a Trinity River Spring Flow Release.

 

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